1. Technical Field of the Disclosure
The present embodiment relates in general to methods for creating organically derived building materials using the growth of fungal tissue. More specifically, the present embodiment relates to a method for growing engineered building materials in the form of a moldable substrate which can be used for a wide range of manufacturing and construction applications.
2. Description of the Related Art
Fungi are a kingdom of organisms which are numerous and diverse, and are distinguished in part by the habits and forms of representative members' vegetative growth and reproduction. While fungi are incredibly diverse in form, habit, and environmental requirements, fungi are easily identifiable by the shared common trait of consuming living or once living organic matter. Like animals, fungi feed on the bodies of other organisms as their primary source of constituent matter and energy, and are the primary decomposers and recyclers of materials on the planet. Fungi are distributed through the depths of the ocean, within and amongst the bodies of all the higher organisms, and have spores that travel to the heights of the atmosphere and out into space. The spores of fungi are resilient enough to enter the vacuum of space and return to earth, growing once again when situated in welcoming terrestrial conditions.
One of the primary forms of material that fungi assist in decomposing are the plants, trees and other organisms that weave airborne carbon into a terrestrial form with energy derived from sunlight. Chlorophyll based organisms transform sunlight into the sugars, carbohydrates and other macromolecules that constitute a plant's various cells, tissues and organs. Many of these sugars in plants are tightly bound within the form of lignin and cellulose, which are composed from an intricately linked glucose based polymer, the constituent element of which comprises the dense structural elements of the plant's body. Many different kinds of fungi have evolved the ability to break down both lignin and cellulose, and transform it into chitin, the resiliently hard molecule that fungi use to build their cell walls. Fungi are both strong and flexible, and are capable of synthesizing (and also metabolizing) a wide range of enzymes, oxidative compounds, alcohols and other caustic chemical agents that can break the strong hydrogen bonds that contribute to the rigidity and structure of cellulose. Many fungi that feed upon cellulose infect and colonize their preferred nutrient source by means of hyphal cells that grow in a vegetative manner from the apical ends of the cell. These hypha are characterized by apical growth patterns that include bifurcations, ramifications and other branching cellular nodes that are capable of secreting and reabsorbing the above mentioned caustic agents, and are capable of breaking down and digesting the hardest known woods. These growing nodes increase the area and potential connectivity of the collective hyphal structures, allowing the fungal cells to infiltrate, connect and modify a wide range of endogenous environments that it might be situated within. The Polypores are a group of fungi that are known for their durability, strength and long life span. The polypores are wide in their geographic distribution and can breakdown and utilize a wide range of plant life that is rich in sources of lignin and cellulose.
In recent years fungi have come to be an accepted material for a range of consumer and building applications, and are increasingly being used in the place of plastics, urethanes and other fossil fuel dependent compounds. In addition to its strength and durability, dried fungus has many other beneficial qualities: it is nontoxic, fire-resistant, mold resistant, water-resistant and a great thermal insulator amongst other salient features. Fungi can be processed with less energy and materials than conventional manufacturing, and can be grown in a way that contributes to good stewardship of renewable resources. Different methods have been developed to utilize the fungi's capabilities for rapidly digesting and transforming a range of biological materials, yet all are due in great part to the physical characteristics of the growing hyphal cells of the fungi, which form a complexly interwoven tissue that is called mycelium.
This mycelial web can be as strong and resilient as wood, and acts as a bonding agent for a wide range of materials that it might be incorporated within. The mycelium itself is remarkably sensitive to local environmental conditions, and the current state of the art is advancing with new means for adjusting and modifying this environment in ways to cause the fungus to grow in a desired manner and with desired characteristics. The state of the art in this field is new and primarily consists of simple molds and laminated substrates, and there is a need for innovative techniques in both the forming, conditioning and manufacturing of the growing fungi and the material that it generates.
Recent advancements in the art include a fungus that is grown for the purposes of providing a polystyrene replacement that is based upon organically derived materials and feedstock. This method involves placing fungus and agricultural or industrial waste products such as rice husks, wheat husks or sawdust into a mold in the form of a panel wherein incubation occurs for several days. During the incubation period the inoculated fungal substrate forms a mycelial network that binds the materials together, slowly solidifying into the shape of the form it was cast within. After incubation, the entire mixture may be dried so that further fungal growth is retarded. The finished panel product exhibits the characteristics of the original materials it was grown from (such as the strength or thermally insulating qualities of the fibers), which are now “glued” together by the fungus. Though a good insulator, this panel must be formed in combination with a laminated back or sandwich of a thin, rigid material when greater tensile strength is desired. The final products made through this process are lightweight, and when its consumer cycle is complete it can be added to landfill or compost due to the sole use of natural ingredients. The product has also been used as a replacement for Styrofoam packaging, both with and without rigid backings, and will soon be available as home and building insulation. This method does not however provide a means for producing environmentally friendly building materials that are also strong and durable enough for the tolerances and demands of many other manufacturing and construction applications than a fragile Styrofoam type formulation.
Another existing system uses mycelium to create materials composed of a hybrid fungal tissue. This method includes the steps for forming an inoculum, which includes a preselected fungus, to form a mixture of a substrate of discrete particles and a nutrient material that is capable of being digested by the fungi. The inoculum is added to the mixture and allows the fungus to digest the nutrient material in the mixture over a period of time sufficient to grow hyphae. The hyphae form a network of interconnected mycelia cells through and around the discrete particles to form a self-supporting composite material. This self-supporting composite material is heated to a temperature sufficient to kill the fungus or otherwise dried to remove any residual water to prevent the further growth of hyphae. The method allows for placing the mixture and inoculum in a mold of any desired shape so that the finished composite material takes on that determined form. The downside to this system is that the fungus must colonize its substrate and incorporate into a solidified form within its carrying mold, limiting production speeds and utilizing one mold per manufactured unit. This method is not conducive to the demands of fast throughput manufacturing and processing that will be needed to make this an economically competitive material.
There are several other methods that have been developed to grow fungus from agricultural and wood industry by-products, using aerated fungal foams, liquid aggregates and the inclusion of secondary reinforcing particles, fibers and other ingredients to aid in making stronger, more resilient materials. Such methods introduce the fungal inoculum into an aerated growth medium, which may include other additional materials such as nutritional supplements or binding and filling agents. The fungal inoculum grows through the foam and binds together its included ingredients into a dense yet flexible material once it has been cured and dried. In one example the method uses different growth mediums such as microcrystalline cellulose mixed with water and nutrients as a support substrate through which the fungal hyphae grow, and as a result rendered into a constituently solidified artifact. After a drying and curing process these fungal foams that include added particles and fibers exhibit increased mechanical strength and flexibility and have other beneficial qualities. This method is limited in application as the size with which one might construct individual components is restricted in volume and mass to small things (2″ cubed). While fungal components may be grown together into larger composite pieces, substrate thickness is usually limited to 6″ in depth due to the anaerobic conditions can arise in samples that are too dense to allow the free exchange of permeable gases between the fungal substrate and the environment it is growing within. This condition gives rise to anaerobic zones within the fungal substrate, making it susceptible to infection by microbes that favor these types of environments. Thus, most of these cured fungal foams that include particles and fibers are limited to being grown in parts that are too small for use in home construction and many other industrial applications.
The environmental benefits of utilizing fungus for the growth of building blocks and other manufacturing materials might be significant in consideration of the impact and potential use of agricultural waste. As a byproduct of growing and producing food worldwide, humans create a vast amount of agricultural waste that would otherwise be unused, returning vast quantities of carbon and other materials during degradation and decomposition. Such agricultural waste may be viewed as food for a fungus. Hence, it can be seen, that there is a need for developing environmentally friendly materials that might replace traditionally used non-biodegradable durable and strong materials, such as plastics and composites. This method would create stronger and dense building blocks, which can be easily molded and cheaply preprocessed to precise geometric specifications. In addition, this method would make it possible to construct highly complex, structured building blocks which might be arranged and joined with each other to comprise structurally engineered manufacturing components and larger artifacts on the scale of buildings from environmentally friendly materials. More importantly, the building blocks created through this method may be completely biodegradable.
While the above benefits are apparent there is also a need for simplification in the prior art. There is a further need to increase performance of the finished product, such as adhesion strength, and compressive capabilities—all without increasing the weight of the material.
The Applicant has discovered that the application of compressive pressure at points throughout the process, either to the lignocellulose based medium or the growing fungal mycelium, results in vastly increased strength, durability and adhesion characteristics. This process additionally speeds production time and allows for the creation of much larger fungal objects.